The present invention generally relates to a method for aligning a moving substrate and a read or write head and, in particular, relates to such a method that ensures that a preselected segment of the moving substrate traverses the read or write head.
In many fields, particularly with the ever increasing use of automated document handing equipment, the ability to write upon or reading from a specific preselected segment of a moving substrate, such as, for example, an envelope, is an important step in the processing of information. One general field wherein this ability is paramount is the field of mail handling. Almost every person and business must, in some fashion, at some time, process mail. In some instances, the volume of mail processed is sufficiently low that the task of reading or writing information from or to each mail piece can be most efficiently performed manually. However, in many instances, the volume of mail pieces processed is so large that the task can be efficiently handled only by automated equipment.
One of the largest mail handling organizations is the United States Postal Service (USPS). In recent years, the USPS, in an effort to provide improved services, has begun using such techniques as the zip code, zip code character readers, postal bar coding and pre-bar coding. In order to maximize the benefits derived from such techniques, it has become necessary for standards to be established for the location of such information on mail documents. For example, in order to maximize the benefits of using an optical character reader (OCR) to ascertain a zip code on an envelope, the zip code must be located within the viewing field of the OCR. Typically, such various location standards are defined with respect to one or more edges of a document being processed, for example, in the instance of processing mail pieces the location may be defined with respect to the lower and leading edges of an envelope or the area of an envelope reserved the address. In order for such systems to function efficiently, the users of the USPS, as well as user of other similar delivery services, must print such information at, or in, these standard locations.
Currently, however, due, to some extent, to the high speed of the available equipment, the alignment of a moving substrate is not a simple task. For example, in the mail handling industry, it is quite common to transport documents, i.e., letters, envelopes, etc., over a predesigned path via a plurality of conveyor belts. Usually, such a path includes one or more changes of direction and may also include, for example, a carousel arrangement for orienting the documents so that a reference edge is proximate a fixed reference fence. The fixed reference fence thus provides a base line wherefrom a read or write head can be positioned with respect to a preselected segment of the document. Typically, in such a system, a mechanism is provided to urge the documents against the fixed reference fence.
Although methods are available that function quite satisfactorily, there nevertheless remain some difficulties. For example, a moving substrate may not be properly aligned, for instance, unless it is delivered, within a reasonable tolerance, to a particular point on a conveyor belt. In such a method, it is quite possible to process large numbers of unaligned documents without immediate detection. In the instance where such misalignment is prior to the time of printing upon an envelope, that envelope may subsequently have information printed thereupon outside of the accepted standard location. Such a misaligned printing reduces the efficiency of not only the mail processing system, but also the efficiency of the mail delivery service.
Consequently, a method for adaptively aligning a moving substrate and a read or write head is highly desirable to improve the efficiency of document handling and, in particular, the processing of mail.